Elimination of monocarbonate from polycarbonate

ABSTRACT

A polycarbonate composition, and process for making same, wherein the monocarbonate and dicarbonate content is eliminated or limited to negligibly low levels by withholding introduction of chain terminator to the reaction mixture until the reaction of dihydroxy and carbonic acid derivative starting materials has run substantially to completion.

BACKGROUND OF THE INVENTION

This invention relates to polycarbonate, and the production thereof,where a chain terminator has been utilized in the manufacturing process,and to molded articles such as compact discs made from suchpolycarbonate.

It is known to produce polycarbonate by the reaction of a dihydroxycompound, particularly an aromatic dihydroxy compound such as the diolBisphenol-A, with a derivative of carbonic acid, such as phosgene. Achain terminator is often added to the reaction mixture for the purposeof regulating the molecular weight of the polycarbonate product. Whenused, the prevalent practice in the art is to include the chainterminator in the monomer mix which is initially charged to the reactionvessel. The dihydroxy compound and the chain terminator are consequentlyboth present in the reaction mixture when it is contacted with thecarbonic acid derivative.

In the manufacture of polycarbonate as described above, molecules ofvarying degrees of polymerization are obtained. The chain terminator isuseful for the purpose of attempting to confine a large percentage ofthe molecules to a preselected molecular weight range. However it hasbeen found that, even when a terminator is used according to thepractice in the art as described above, not all molecules conform to thepreselected weight range, and some molecules of extremely low molecularweight (carbonate byproducts) can still result.

Carbonate byproducts, being the smallest of the molecules resulting fromthe production of polycarbonate, have the lowest respective boilingpoints and are therefore the most likely to exist in vapor phase. Thepresence of carbonate byproducts in vapor phase becomes a considerationwhen polycarbonate is, for example, being extruded or molded, or heatedfor any other purpose. Accordingly, it would be desirable to prevent orlimit the formation of carbonate byproducts in polycarbonate, andthereby assist in the manufacture of a polycarbonate product wherein thegreatest possible percentage of the molecules fall within thepreselected molecular weight range which it is the purpose of theterminator to achieve.

SUMMARY OF THE INVENTION

In one aspect, this invention is a polycarbonate composition which isfree of, or substantially free of, monocarbonate. In another aspect,this invention is a polycarbonate composition which contains no morethan Z ppm of dicarbonate where Z is given by log₁₀(Z)=14.045216-2.4921524log₁₀ (Mw), and "Mw" is the weight averagemolecular weight of said composition. In yet another aspect, thisinvention is a process for making polycarbonate wherein monocarbonatedoes not form, or substantially does not form. In yet another aspect,this invention is a process for making a polycarbonate compositionwherein dicarbonate does not form in an amount in excess of Z ppm whereZ is as given above. In yet another aspect, this invention is a processfor preventing, or substantially preventing, the formation ofmonocarbonate in polycarbonate. In yet another aspect, this invention isa process for limiting the formation of dicarbonate, in a polycarbonatecomposition, to no more than Z ppm where Z is as given above.

It has surprisingly been discovered that, in the production ofpolycarbonate by the reaction of a dihydroxy compound with a carbonicacid derivative and a chain terminator, formation of monocarbonate inthe reaction product can be prevented, and the formation of dicarbonatecan be limited to a low amount related to the molecular weight of thepolycarbonate, by withholding the addition of chain terminator to thereaction mixture until the reaction of the dihydroxy compound with thecarbonic acid derivative is complete, as indicated by an increase of theheat of reaction to a constant level. ("Monocarbonate" and "dicarbonate"are carbonate byproducts which are more particularly definedhereinbelow.) Polycarbonate which is free or substantially free ofmonocarbonate and/or which contains the aforesaid reduced level ofdicarbonate is an improved product, and the process for makingpolycarbonate of such quality is correspondingly an improved process, incomparison to the known art. The presence of such carbonate byproducts,especially monocarbonate, often causes partial plugging of mold ventsand thus uneven flow of molten extrudate into all parts of a moldcavity, leaving imperfections in finished articles made of polycarbonateby injection molding, e.g., a phenomenon known as "ghost lines" or"ghosting" in the production of compact discs.

The improved polycarbonate of this invention, and polycarbonate made bythe improved process hereof, is useful, for example, in the productionof moldings, films, fibers optical products and shaped articles ofvirtually all varieties, especially for compact discs, appliance andinstrument housings, and other items for the electronics and automotiveindustries.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

"Monocarbonate", when used in this description and in the claimsappended hereto, means a carbonate byproduct which can result during theproduction of polycarbonate, when a dihydroxy compound, a carbonic acidderivative and a chain terminator make up the monomer mix, from a sidereaction directly between the chain terminator and the carbonic acidderivative. Monocarbonate contains one carbonyl carbon and twoterminator units and therefore contains no dihydroxy units.Correspondingly, "dicarbonate" as used in the description and claimshereof means a carbonate byproduct resulting when two carbonic acidunits have been coupled by a dihydroxy unit but then have been stoppedfrom further such coupling by the terminator. Dicarbonate contains onecarbonyl carbon and terminator unit linked to a second carbonyl carbonand terminator unit by a dihydroxy unit. Monocarbonate is sometimes alsoreferred to herein as "L_(o) ", signifying a linear carbonate byproductcontaining no dihydroxy units, and dicarbonate is correspondinglysometimes referred to herein as "L₁ ".

For example, in the case where Bisphenol-A is phosgenated in thepresence of para-t-butyl phenol ("PTBP") as a terminator, the compoundreferred to as L_(o) (no Bisphenol-A units, i.e. the monocarbonate) willresult when PTBP reacts directly with phosgene, L_(o) in such case isdi(tert-butyl) phenyl carbonate. If phenol had been used as theterminator, L_(o) would be diphenyl carbonate, and if 4-(tert-octyl)phenol had been used as the terminator, L_(o) would bedi-4-(tert-octyl)-phenyl carbonate. These phenolic carbonates have thegeneral formula ##STR1## where R, in the cases mentioned above, ist-butyl, H or tert-octyl, respectively. Correspondingly, when each endof one Bisphenol-A unit has reacted with a phosgene molecule beforeterminator has capped those phosgene molecules, the compound referred toas L₁ (one Bisphenol-A unit, i.e. the dicarbonate) is produced. L₁ insuch case has the formula ##STR2## where R would be as set forth aboveaccording to the terminator used.

The compositions of this invention, and processes for making same,wherein L_(o) forms only in an amount less than 100 ppm, preferablyforms only in a negligible, insignificant quantity or amount (e.g., lessthan 20 ppm), more preferably substantially does not form (e.g., formsin an amount less than 3 ppm), and most preferably does not form, andwherein L₁ in excess of Z ppm does not form where Z in given by log₁₀(Z)=14.045216-2.4921524log₁₀ (Mw), and "Mw" is the weight averagemolecular weight of said composition, are obtained by adding chainterminator during polycarbonate production in an advantageous mannerimproved over the art.

It is known in the art to produce polycarbonate by the reaction of acarbonic acid derivative with a dihydroxy compound, such as an aliphaticor aromatic diol. Suitable dihydroxy compounds are those wherein thesole reactive group are the two hydroxyl groups, such as (1) a compoundrepresented by the general formula HO--R² --OH where R² is anysubstituted or unsubstituted arylene or divalent aliphatic (cyclic orchain) hydrocarbon radical, or a mixture of more than one of saidradicals, or (2) variously bridged, substituted or unsubstitutedaromatic diols represented by the general formula ##STR3## where

(a) A is a divalent hydrocarbon radical containing 1-15 carbon atoms, oris a mixture of more than one of such radicals, or is ##STR4##

(b) X is independently hydrogen, chlorine, bromine or fluorine or is amonovalent hydrocarbon radical such as an alkyl group of 1-4 carbons, anaryl group of 6-8 carbons such as phenyl, tolyl or xylyl, an alkoxygroup of 1-4 carbons or an aryloxy group of 6-8 carbons: and

(c) n is 0 or 1.

The dihydroxy compounds employed in this invention advantageouslyinclude the trityl diols described in U.S. Pat. Nos. 3,036,036,3,036,037, 3,036,038 and 3,036,039; thebis(ar-hydroxy-phenyl)alkylidenes (often called the bisphenol-A typediols), including their aromatically and aliphatically susbtitutedderivatives, such as disclosed in U.S. Pat. Nos. 2,999,835, 3,038,365,3,334,154 and 4,299,928; aromatic diols such as described in U.S. Pat.No. 3,169,121; dihydroxy benzenes; resorcinol; hydroquinone; halo- andalkyl-substituted dihydroxy benzenes; and dihydroxy diphenyl sulfidessuch as bis(4-hydroxyphenyl) sulfide. Two or more different dihydroxycompounds may be used in the event a carbonate copolymer or interpolymerrather than a homopolymer is desired. Each of the above mentionedpatents is incorporated herein in its entirety.

One group of suitable dihydroxy compounds includes the followingdihydric phenols:

1,1-bis(4-hydroxyphenyl)-1-phenyl ethane

1,1-bis(4-hydroxyphenyl)-1,1-diphenyl methane

1,1-bis(4-hydroxyphenyl)cyclooctane

1,1-bis(4-hydroxyphenyl)cycloheptane

1,1-bis(4-hydroxyphenyl)cyclohexane

1,1-bis(4-hydroxyphenyl)cyclopentane

2,2-bis(3-propyl-4-hydroxyphenyl)decane

2,2-bis(3,5-dibromo-4-hydroxyphenyl)nonane

2,2-bis(3,5-isopropyl-4-hydroxyphenyl)nonane

2,2-bis(3,ethyl-4-hydroxyphenyl)octane

4,4-bis(4-hydroxyphenyl)heptane

3,3-bis(3-methyl-4-hydroxyphenyl)hexane

3,3-bis(3,5-difluoro-4-hydroxyphenyl)butane

2,2-bis(3,5-difluoro-4-hydroxyphenyl)butane

1,1-bis(3-methyl-4-hydroxyphenyl)ethane

1,1-bis(4-hydroxyphenyl)methane

2,2-bis(4-hydroxyphenyl)propane ("Bisphenol-A" or "Bis-A")

1,1-bis(4-hydroxyphenyl)-1-phenyl ethane ("Bisphenol-A-P" or "Bis-A-P")

2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane ("Tetrabromo Bisphenol-A")

2,2-bis(3,5-dimethyl-4-hydroxylphenol)propane ("TetramethylBisphenol-A").

Another group of dihydroxy compounds useful in the practice of thepresent invention includes the following dihydroxyldiphenyl sulfoxides:bis(3,5-diisopropyl-4-hydroxyphenyl)sulfoxide

bis(3-methyl-5-ethyl-4-hydroxyphenyl)sulfoxide

bis(3,5-dibromo-4-hydroxyphenyl)sulfoxide

bis(3,5-dimethyl-4-hydroxyphenyl)sulfoxide

bis(3-methyl-4-hydroxyphenyl)sulfoxide

bis(4-hydroxyphenyl)sulfoxide.

Another group of dihydroxy compounds which may be used in the practiceof this invention includes the following dihydroxaryl sulfones:

bis(3,5-diisopropyl-4-hydroxyphenyl)sulfone

bis(3-methyl-5-ethyl-4-hydroxyphenyl)sulfone

bis(3-chloro-4-hydroxyphenyl)sulfone

bis(3,5-dibromo-4-hydroxyphenyl)sulfone

bis(3,5-dimethyl-4-hydroxyphenyl(sulfone

bis(3-methyl-4-hydroxyphenyl)sulfone bis(4-hydroxyphenyl)sulfone.

Another group of dihydroxy compounds useful in the practice of thisinvention includes the following dihydroxydiphenyls:

3,3',5,5'-tetrabromo-4,4'-dihydroxydiphenyl

3,3'-dichloro-4,4'-dihydroxydiphenyl

3,3'-diethyl-4,4'-dihydroxydiphenyl

3,3'-dimethyl-4,4'-dihydroxydiphenyl

p,p'-dihydroxydiphenyl.

Another group of dihydroxy compounds which may be used in the practiceof this invention includes the following dihydric phenol ethers:

bis(3-chloro-5-methyl-4-hydroxyphenyl)ether

bis(3,5-dibromo-4-hydroxyphenyl)ether

bis(3,5-dichloro-4-hydroxyphenyl)ether

bis(3-ethyl-4-hydroxyphenyl)ether

bis(3-methyl-4-hydroxyphenyl)ether

bis(4-hydroxyphenyl)ether.

The dihydroxy compounds mentioned above are suitable for the productionof polycarbonate in the practice of this invention, and among those themost preferred are Bisphenol-A, Bisphenol-A-P, Tetrabromo Bisphenol-Aand Tetramethyl Bisphenol-A. It has been found that polycarbonateproduced from Bisphenol-A-P or Tetrabromo Bisphenol-A advantageously hasa high glass transition temperature and other favorable high temperatureproperties.

A carbonic acid derivative suitable for use in this invention containsleaving groups which can be displaced from the carbonyl carbon in attackby the anion of a dihydroxy compound, and includes but is notnecessarily limited to diesters of carbonic acid, and the carbonylhalides, of which the most preferred is phosgene (COCl₂).

The reaction to produce polycarbonate will proceed at, but is notrestricted to, ambient temperature. Its rate will increase, especiallytoward the end of the reaction, if it is run at a somewhat elevatedtemperature of about 50° C. to about 125° C. More complete reactionbetween the dihydroxy compound and the carbonic acid derivative willoccur if the reaction is run in the presence of a base. A starting pH ofat least about 10 is preferred, with a pH in the range of about 11 toabout 14 being more preferred. The presence of base in the reactionmixture helps convert the dihydroxy compound to its corresponding anion,which then reacts rapidly with the carbonic acid derivative. Suitablebases are the alkali or alkaline earth carbonates, oxides or hydroxides,or an organic base such as pyridine or an amine, with the most preferredof those being sodium hydroxide. The base may be added continuously orin incremental quantities during the reaction to maintain or restore thedesired pH. The carbonate linkage is formed, and polymer growth occurs,when both leaving groups are displaced from the carbonic acid derivativein reaction with the anion formed from the dihydroxy compound

If an organic base such as pyridine is used, the reaction could occur ina homogeneous solution containing the dihydroxy compound and thecarbonic acid derivative, which solution would typically also contain anorganic solvent such as the chlorinated hydrocarbon chloro benzene. Thismethod, usually referred to as the solution process, is not as common asthe interfacial process, wherein polycarbonate is produced in atwo-phase system where the dihydroxy compound is dissolved or suspendedin an aqueous solution of an inorganic base such as sodium hydroxide. Anorganic solvent capable of dissolving the polycarbonate product, such asthe chlorinated hydrocarbon methylene chloride, makes up the otherphase. This reaction mixture is contacted with the carbonic acidderivative, and the resulting polycarbonate product will accumulate inthe organic phase. In the case of either method, the solution containingthe product is neutralized with acid and washed free of electrolytes,and the polycarbonate is then recovered by various known methods. Thepolymer resulting from the production methods described above isgenerally characterized by a repeating unit of the formula ##STR5##where --O--R³ --O-- is the residue of the dihydroxy compound utilized.The polycarbonate chain contains up to about 200 such units, with thepreferred chain length being about 20 to about 75 such units.

Methods for producing polycarbonate, as generally described above, anddihydroxy compounds and carbonic acid derivatives suitable for use asstarting materials in the reaction mixture, are more particularlydescribed in Moyer, U.S. Pat. Nos. 2,970,131 (Union Carbide); Schnell,3,028,365 (Bayer AG); Freitag, 4,269,964 (Bayer AG) and Glass, 4,529,791(Dow), each of which is incorporated as a part hereof in its entirety.

The improvements which are the subject of this invention relate to thetiming of the addition of chain terminator to a polycarbonate, reactionmixture containing a dihydroxy compound and a carbonic acid derivative.A terminator is a monofunctional compound containing a functional group,frequently a hydroxy group, which .[.will produce an anion capable ofdisplacing.]. .Iadd.is reactive with .Iaddend.an unreacted hydroxy orcarbonic acid ester group which remains on the end of a polymer chain.Representative of the terminators which are used for such purpose in theproduction of polycarbonate are phenol and the derivatives thereof,saturated aliphatic alcohols, metallic sulfites, alkyl acid chlorides,trialkyl- or triaryl-silanols, monohalosilanes, amino alcohols, trialkylalcohols, aniline and methylaniline. Of these, phenol, PTBP and4-(1,1,3,3-tetramethylbutyl)-phenol (4-tert-octyl phenol) are the mostpreferred. Of the three preferred terminators just mentioned,4-tert-octyl phenol has the highest boiling point and is therefore theleast volatile.

When a terminator is used, the prevalent practice in the art is to admixthe terminator with the monomers before the dihydroxy compound has beencontacted with the carbonic acid derivative. Any terminator anioncapable of attacking .[.an hydroxy or.]. .Iadd.a .Iaddend.carbonic acidester end group on a polymer chain is also capable of undesirably either(1) attacking unreacted molecules of the initial charge of the carbonicacid derivative, or (2) displacing end groups before a chain has anopportunity to grow to the desired length. The practice in the art ofadding chain terminator to the reaction mixture prior to introduction ofthe carbonic acid derivative consequently allows the formation ofcarbonate byproducts by the occurrence of both of the aforesaid results.For example, the tendency of monocarbonate to form can be seen fromCampbell, U.S. Pat. No. 4,384,108 (G.E.), which is incorporated as apart hereof in its entirety, wherein (in Table 11) a polycarbonateproduct containing 350 ppm of diphenyl carbonate is reported.

Carbonate byproduct content in excess of that specified for the improvedproduct hereof typically detracts from the desirable properties andqualities of polycarbonate and, in most applications, may be seen as animpurity therein. For example, when polycarbonate produced byphosgenating Bisphenol-A in the presence of PTBP is injection molded,plate-out (a powdery residue) frequently appears on the mold and/or theobject being molded. Because of the undesirable effect on the quality ofthe polycarbonate product caused by the presence of L_(o) and L₁, theL_(o) content of the improved polycarbonate of this invention (and ofthe polycarbonate product of the improved process of this invention) atany molecular weight should be less than 100 ppm. Preferably, theproduct will contain only a negligible, insignificant quantity or amountof L_(o) (e.g., less than 20 ppm), more preferably the product will besubstantially free of L_(o) (e.g., contain less than 3 ppm thereof) andmost preferably the product will be free of L_(o). The L₁ content shouldbe limited to a low level related to the molecular weight of thepolycarbonate, for example, the polycarbonate should contain no morethan Z ppm of dicarbonate where Z is given by log₁₀(Z)=14.045216-2.4921524 log₁₀ (Mw), and "Mw" is the weight averagemolecular weight of the polycaxbonate composition.

Because of the desire to prevent the formation of and the desire tolimit the formation of L₁ to low levels, an advantageous method for theproduction of polycarbonate has been discovered which is improved overthe practice in the art. This improvement is accomplished by withholdingaddition of chain terminator to the reaction mixture until reaction ofthe dihydroxy compound with the carbonic acid derivative has proceededto completion, as indicated by an increase in the heat of reaction to aconstant level. (Methods for analyzing the temperature profile of apolycarbonate formation reaction are known in the art, as shown forexample in Brunelle, U.S. Pat, No. 4,722,995 (G.E.), which isincorporated herein in its entirety.) Because the terminator is notpresent in the reaction mixture, premature attack by it on the unreactedportion of the carbonic acid derivative is not possible, therebylimiting the formation of L_(o) to less than 100 ppm, preferablylimiting the formation of L_(o) to a negligible, insignificant quantityor amount (e.g., to less than 20 ppm), more preferably substantiallypreventing the formation of L_(o) (e.g., L_(o) formation of less than 3ppm), and most preferably preventing the formation of L_(o) ; with theadditional result of limiting the formation of dicarbonate to no morethan Z ppm, where Z is given by log₁₀ (Z)=14.045216-2.4921524log₁₀ (Mw),and "Mw" is the weight average molecular weight of said polycarbonate.This process, the nature of the product resulting therefrom, and theimprovements embodied thereto, are more particularly illustrated by thedata set forth below.

EXAMPLE 1

Monomer solution is prepared by adding 1,393 grams of 34% caustic (i.e.473.62 grams of NaOH) to 1,350 grams of Bisphenol-A and 6,959 grams ofwater. This monomer solution is contacted with phosgene and methylenechloride solvent in a 3/8 inch (9.52 mm) diameter tubular reactor with a2 minute residence time. Three 6 inch (15.24 cm) long and one 12 inch(30.48 cm) long [3/8 inch (9.52 mm) diameter] inline mixers were used toimprove gas/liquid contacting. The monomer solution flow rate is set at29 grams/minute. Phosgene flow rate is set at 2.4 grams/minute, andmethylene chloride flow rate is set at 17 grams/minute. Thepolycarbonate oligomers formed from this process are separated from theaqueous layer. To 24 grams of the oligomers are added 21 grams of waterand 2.42 grams of 10% solution of PTBP in methylene chloride. Thismixture is placed in a 4 ounce (113.65 ml) glass bottle and shaken in amechanical shaker for 5 minutes. This represents plug flow mixing of theterminator with the oligomers. After 5 minutes, 2.45 grams of 50%caustic (i.e. 1.225 grams NaOH) are added, and the mixture is shaken foranother 5 minutes. After this 35 grams of methylene chloride and 1.75grams of 1.5% solution of TEA (triethylamine) in methylene chloride areadded, and the mixture is shaken until the completion of polymerizationas indicated by the disappearance of the chloroformates. Thepolycarbonate product has a molecular weight of 17,400 and an L₁ contentof 3,000 ppm, and L_(o) is non-detectable therein.

EXAMPLE 2

The procedure of Example 1 is repeated except that 1.09 grams of 10%solution of PTBP in methylene chloride are used instead of 2.24 grams.The polycarbonate product has a molecular weight of 31,200 and L₁content of 700 ppm, and L_(o) is non-detectable therein.

EXAMPLE 3

A monomer solution consisting of 0.65 moles of Bisphenol-A, and 2 molesof NaOH per mole of Bisphenol-A, is phosgenated in a 2 inch (5.08 cm)pipe having three 5 inch (12.70 cm) mixers with a one minute totalresidence time during mixing. Phosgene addition to the reaction mixtureis at the rate of 128 pounds (58.06 kg) per hour. 0.053 Moles of PTBPper mole of Bisphenol-A are added to the reaction mixture after it haspassed the second mixer. 50% By weight caustic is then added to thereaction mixture at the rate of 93 pounds (42.18 kg) per hour. Aftercompletion of mixing, the reaction mixture is finished in a stirred tankwith a three minute residence time. Methylene chloride, at the rate of600 pounds (272.15 kg) per hour, is then added to the stirred tank.After the reaction mixture is cooled, chain coupling catalyst(triethylamine) is added to complete the polymerization. Thepolycarbonate produced thereby has a molecular weight of 19,385, anL_(o) content of 16 ppm and an L₁ content of 1,110 ppm.

EXAMPLE 4

The procedure of Example 1 is repeated except that phenol is used as thechain terminator instead of PTBP. The polycarbonate product has amolecular weight of 17,500 and an L₁ content of 3,200 ppm, and L_(o) isnon-detectable therein.

EXAMPLE 5

The procedure of Example 1 is repeated except that 4-(tert-octyl) phenol("PTOP") is used as the chain terminator instead of PTBP. Thepolycarbonate product has a molecular weight of 16,323 and an L₁ contentof 1,840 ppm, and L_(o) is non-detectable therein.

EXAMPLE 6

Monomer solution is prepared by adding 1,420 grams of 34% caustic (i.e.482.80 grams of NaOH) to 1,400 grams of Bisphenol-A-P and 7,316 grams ofwater. This monomer solution is contacted with phosgene and methylenechloride solvent in a 3/8 inch (9.52 mm) diameter tubular reactor with a2 minute residence time. Three 6 inch (15.24 cm) long and one 12 inch(30.48 cm) long [3/8 inch (9.52 mm) diameter] inline mixers are used toimprove gas/liquid contacting. The monomer solution flow rate is set at30 grams/minute. Phosgene flow rate is set at 1.5 grams/minute, andmethylene chloride flow rate is set at 21 grams/minute. Thepolycarbonate oligomers formed from this process are separated from theaqueous layer. To 19 grams of the oligomers are added 37 grams of waterand 0.67 grams of 10% solution of PTBP in methylene chloride. Thismixture is placed in a 4 ounce (113.65 ml) glass bottle and shaken in amechanical shaker for 5 minutes. This represents plug flow mixing of theterminator with the oligomers. After 5 minutes, 2.1 grams of 50% caustic(i.e. 1.05 grams NaOH) are added, and the mixture is shaken for another5 minutes. After this 21 grams of methylene chloride and 0.27 grams of1.5% solution of TEA (triethylamine) in methylene chloride are added,and the mixture is shaken until the completion of polymerization asindicated by the disappearance of the chloroformates. The polycarbonateproduct has a molecular weight of 21,100 and an L₁ content of 860 ppm,and L_(o) is non-detectable therein.

EXAMPLE 7

Monomer solution is prepared by adding 1,420 grams of 34% caustic (i.e.482.80 grams of NaOH) to 1,400 grams of Bisphenol-A-P and 7,316 grams ofwater. This monomer solution is contacted with phosgene and methylenechloride solvent in a 3/8 inch (9.52 mm) diameter tubular reactor with a2 minute residence time. Three 6 inch (15.24 cm) long and one 12 inch(30.48 cm) long [3/8 inch (9.52 mm) diameter] inline mixers were used toimprove gas/liquid contacting. The monomer solution flow rate is set at30 grams/minute. Phosgene flow rate is set at 1.5 grams/minute, andmethylene chloride flow rate is set at 21 grams/minute. Thepolycarbonate oligomers formed from this process are separated from theaqueous layer. To 27 grams of the oligomers are added 29 grams of waterand 0.67 grams of 10% solution of PTBP in methylene chloride. Thismixture is placed in a 4 ounce (113.65 ml) glass bottle and shaken in amechanical shaker for 5 minutes. This represents plug flow mixing of theterminator with the oligomers. After 5 minutes, 2.1 grams of 50% caustic(i.e. 1.05 grams NaOH) are added, and the mixture is shaken for another5 minutes. After this 21 grams of methylene chloride and 0.27 grams of1.5% solution of TEA (triethylamine) in methylene chloride are added,and the mixture is shaken until the completion of polymerization asindicated by the disappearance of the chloroformates. The polycarbonateproduct has a molecular weight of 30,600 and an L₁ content of 150 ppm,and L_(o) is non-detectable therein.

Measurement of the quantity of L_(o) and L₁ in the polycarbonate samplesmade in the foregoing examples was accomplished by high-performancereverse-phase liquid chromatography. The products were analyzed on aHewlett Packard 1090 chromatograph, using a 15 cm×4 mm I.D. column,packed with Spherisorb ODS II three micron packing. Tetrahydrofuran/H₂ Owas used as the carrier solvent, UV absorbtion at 264±5 nm wasdetermined for each oligomer as it eluted from the column. Absorbtionpeaks were compared to those generated by standardization samplescontaining carefully measured amounts of mono- and dicarbonate.

In Examples 1-2 and 4-7, L_(o) content of below 50 ppm was notdetectable by this method of measurement. The "ND" (non-detectable)result reported (in Table I) for L_(o) content in those examplestherefore indicates that L_(o) content was less than 50 ppm. In Example3, and with respect to an additional analysis of the product of Example2, the limit of detection was lowered by precipitating the polycarbonateproduct to be analyzed from a methylene chloride solution with anantisolvent in which the polymeric polycarbonate is not soluble (such asn-heptane), evaporating the supernatant liquid, and then redissolvingthe polycarbonate in the chromatographic solvent, Tetrahydrofuran. Thelimit of detection of L_(o) when these additional measures were takenwas 3 ppm. L_(o) was again non-detectable in the product of Example 2when it was analyzed using the additional precipitation, and the L_(o)content was thus shown to in fact be less than 3 ppm, not just less than50 ppm.

All of the foregoing examples, which are summarized below in Table I,demonstrate that, when chain terminator is utilized in the production ofpolycarbonate by the reaction of a dihydroxy compound with a carbonicacid derivative, if the reaction between the dihydroxy compound and thecarbonic acid derivative is allowed to run to completion before theterminator is added to the reaction mixture, the formation of L_(o) isprevented, or is substantially prevented, yielding a polycarbonateproduct which is purified of, or is free, or substantially free, ofL_(o). Additionally, the formation of L₁ is limited to no more than anamount Z in ppm where Z is given by log₁₀ (Z)=14.045216-2.4921524 log₁₀(Mw), and "Mw" is the weight average molecular weight of thepolycarbonate composition. (While this relationship has been derivedfrom a log-log regression plot based on the data resulting fromproduction of polycarbonate by reacting Bisphenol-A with phosgene andPTBP, the corresponding relationship, can be deprived by one skilled inthe art, with respect to polycarbonate based on other startingmaterials, by following the same approach. The value "Z", as determinedby the equation set forth above, is given in Table I for the product ofExamples 1, 2 and 3, each of which is the product of the reaction ofBisphenol-A, phosgene and PTBP.)

                  TABLE I                                                         ______________________________________                                              Dihydroxy Termi-   M.W.   L.sub.0                                                                            L.sub.1                                                                             "Z"                                Ex.   Compound  nator    grams  ppm  ppm   ppm                                ______________________________________                                        1     Bis-A     PTBP     17,400 ND   3,000 3,000                              2     Bis-A     PTBP     31,200 ND   700   700                                3     Bis-A     PTBP     19,385 16   1,110 2,292                              4     Bis-A     Phen.    17,500 ND   3,200 --                                 5     Bis-A     PTOP     16,323 ND   1,840 --                                 6     Bis-A-P   PTBP     21,100 ND   860   --                                 7     Bis-A-P   PTBP     30,600 ND   150   --                                 ______________________________________                                    

Since this invention is based on the reproducable step of withholdingaddition of chain terminator to the reaction mixture until the reactionof the dihydroxy compound and the carbonic acid derivative has run tocompletion, as indicated by an increase of the heat of reaction to aconstant level, the improved polycarbonate product described herein isobtainable with virtually any combination of the dihydroxy compounds,carbonic acid derivatives and chain terminators mentioned herein. Forexample, in a given situation it might be desired to make polycarbonateusing a dihydroxy compound such as Bisphenol-A-P or TetrabromoBisphenol-A rather than Bisphenol-A. Or, it might be desired to usephenol or p-t-octyl phenol as the terminator in such polycarbonaterather than p-t-butyl phenol.

It is within the skill in the art to practice this invention in numerousmodifications and variations in light of the above teachings. It is,therefore, to be understood that changes may be made in the variousdescribed embodiments of this invention without departing from thespirit and scope of this invention as defined by the appended claims.For example, fillers and modifiers have found wide usage inpolycarbonate products. These might include reinforcing agents,pigments, lubricants, mold release agents, clays, carbon black,asbestos, and stabilizers such as glass fibers or to retard UVdegredation or impart ignition resistance. Addition of any one or moreof those in the polycarbonate product and process of this inventionwould not be a departure therefrom. Additionally, there are numerousaspects of polycarbonate production, other than those described herein,which are known and frequently employed by those skilled in the art.There are, for example, many known kinds of solvents, chain couplingcatalysts, branching agents, reducing agents and product recoverytechniques which are utilized in the production of polycarbonate. Oneskilled in the art could readily utilize one or more of the aforesaid inthe practice of this invention without departing from the scope thereof.

What is claimed is: .[.1. A composition comprising a carbonate polymerwhich is the product of the reaction of a dihydroxy compound with acarbonic acid derivative and a chain terminator containing a hydroxygroup, which composition is free of monocarbonate..]..[.2. A compositioncomprising a carbonate polymer which is the product of the reaction of adihydroxy compound with a carbonic acid derivative and a chainterminator containing a hydroxy group, which composition contains only anegligible, insignificant amount of monocarbonate..]..[.3. A compositioncomprising a carbonate polymer which is the product of the reaction ofBisphenol-A with phosgene and para-t-butyl phenol, and which containsonly a negligible, insignificant amount of monocarbonate and contains nomore than Z ppm of dicarbonate where Z is given by log₁₀(Z)=14.045216-2.4921524log₁₀ (Mw), and "Mw" is the weight averagemolecular weight of said composition..]..[.4. A composition comprising acarbonate polymer which is the product of the reaction of Bisphenol-Awith phosgene and para-t-butyl phenol, and which contains less than 100ppm of monocarbonate and contains no more than Z ppm of dicarbonatewhere Z is given by log₁₀ (Z)=14.045216-2.4921524log₁₀ (Mw), and "Mw" isthe weight average molecular weight of said composition..]..[.5. Acomposition comprising a carbonate polymer which is the product of thereaction of a dihydroxy compound, other than Bisphenol-A, with acarbonic acid derivative and a chain terminator containing a hydroxygroup, which composition contains less than 100 ppm ofmonocarbonate..]..[.6. A composition comprising a carbonate polymerwhich is the product of the reaction of a dihydroxy compound with acarbonic acid derivative and a chain terminator containing a hydroxygroup, other than para-t-butyl phenol, which composition contains lessthan 100 ppm of monocarbonate..]..[.7. The composition of claim 1, 2 or5 wherein the chain terminator is para-t-butyl phenol, phenol or4-(tert-ocyl) phenol..]..[.8. The composition of claim 1, 2 or 6 whereinthe dihydroxy compound is Bisphenol-A, Bisphenol-A-P, TetrabromoBisphenol-A or Tetramethyl Bisphenol-A..]..[.9. The composition of claim1 or 2 wherein the dihydroxy compound is Bisphenol-A and the chainterminator is para-t-butyl phenol..].10. .[.A.]. .Iadd.An interfacial.Iaddend.process for making polycarbonate comprising .Iadd.the steps insequence of .Iaddend..[.(a) forming a reaction mixture which comprises adihydroxy compound, a carbonic acid derivative, a solvent, andsufficient base to bring about the formation of polycarbonate, and (b)employing in said reaction mixture a chain terminator, containing ahydroxy group, such that monocarbonate does not form.]. (.Iadd.a)forming a reaction mixture which comprises a dihydroxy compound,phosgene, and organic solvent, and sufficient aqueous base to bringabout the formation of polycarbonate; (b) employing in said reactionmixture a chain terminator, containing a hydroxy group, such thatmonocarbonate forms only in an amount less than 100 ppm by adding saidchain terminator to the reaction mixture when the reaction between saiddihydroxy compound and said phosgene to form polycarbonate is complete;(c) cooling the reaction mixture; and (d) adding a chain couplingcatalyst to the polycarbonate forming reaction mixture.Iaddend.. .[.11.A process for making polycarbonate comprising(a) forming a reactionmixture which comprises a dihydroxy compound, a carbonic acidderivative, a solvent, and sufficient base to bring about the formationof polycarbonate, and (b) employing in said reaction mixture a chainterminator, containing a hydroxy group, such that monocarbonate formsonly in a negligible, insignificant amount..]..[.12. A process formaking polycarbonate comprising(a) forming a reaction mixture whichcomprises Bisphenol-A, phosgene, a solvent, and sufficient base to bringabout the formation of polycarbonate, and (b) employing para-t-butylphenol in said reaction mixture such that monocarbonate forms only in anegligible, insignificant amount, and dicarbonate in excess of Z ppmdoes not form where Z is given by log₁₀ (Z)=14.045216-2.4921524log₁₀(Mw), and "Mw" is the weight average molecular weight of saidpolycarbonate..]..[.13. A process for making polycarbonate comprising(a)forming a reaction mixture which comprises a dihydroxy compound, acarbonic acid derivative, a solvent, and sufficient base to bring aboutthe formation of polycarbonate, and (b) employing in said reactionmixture a chain terminator, containing a hydroxy group, such thatmonocarbonate forms only in an amount less than 100 ppm..]..[.14. Aprocess for making polycarbonate comprising(a) forming a reactionmixture which comprises Bisphenol-A, phosgene, a solvent, and sufficientbase to bring about the formation of polycarbonate, and (b) employingpara-t-butyl phenol in said reaction mixture such that monocarbonateforms only in an amount less than 100 ppm and dicarbonate in excess of Zppm does not form where Z is given by log₁₀ (Z)=14.045216-2.4921524log₁₀(Mw), and "Mw" is the weight average molecular weight of saidpolycarbonate..].15. The process of claim 10.[., 11 or 13.]. wherein thedihydroxy compound is Bisphenol-A, Bisphenol-A-P, Tetrabromo Bisphenol-Aor Tetramethyl Bisphenol-A. .[.16. In the manufacture of polycarbonatewhich is the product of contacting a dihydroxy compound with a carbonicacid derivative and a chain terminator containing a hydroxy group, aprocess for preventing the formation of monocarbonate, comprising thesteps in sequence of(a) contacting said dihydroxy compound with saidcarbonic acid derivative in a reaction mixture containing a solvent andsufficient base to give such reaction mixture a pH of greater than about10, thereby forming polycarbonate, and (b) adding said chain terminatorto said reaction mixture when the heat of said reaction has increased toa constant level..]..[.17. In the manufacture of polycarbonate which isthe product of contacting a dihydroxy compound with a carbonic acidderivative and a chain terminator containing a hydroxy group, a processfor limiting the formation of monocarbonate to a negligible,insignificant amount, comprising the steps in sequence of (a) contactingsaid dihydroxy compound with said carbonic acid derivative in a reactionmixture containing a solvent and sufficient base to give such reactionmixture a pH of greater than about 10, thereby forming polycarbonate,and (b) adding said chain terminator to said reaction mixture when theheat of said reaction has increased to a constant level..]..[.18. In themanufacture of polycarbonate which is a product of contactingBisphenol-A with phosgene and para-t-butyl phenol, a process forlimiting the formation of monocarbonate to a negligible, insignificantamount and limiting the formation of dicarbonate to no more than Z ppm,where Z is given by log₁₀ (Z)=14.045216-2.4921524log₁₀ (Mw), and "Mw" isthe weight average molecular weight of said polycarbonate, comprisingthe steps in sequence of(a) contacting Bisphenol-A with phosgene in areaction mixture containing a solvent and sufficient base to give suchreaction mixture a pH of greater than about 10, thereby formingpolycarbonate, and (b) adding para-t-butyl phenol to said reactionmixture when the heat of said reaction has increased to a constantlevel..]..[.19. In the manufacture of polycarbonate which is the productof contacting a dihydroxy compound with a carbonic acid derivative and achain terminator containing a hydroxy group, a process for limiting theformation of monocarbonate to less than 100 ppm, comprising the steps insequence of (a) contacting said dihydroxy compound with said carbonicacid derivative in a reaction mixture containing a solvent andsufficient base to give such reaction mixture a pH of greater than about10, thereby forming polycarbonate, and (b) adding said chain terminatorto said reaction mixture when the heat of said reaction has increased toa constant level..]..[.20. In the manufacture of polycarbonate which isa product of contacting Bisphenol-A with phosgene and para-t-butylphenol, a process for limiting the formation of monocarbonate to lessthan 100 ppm and limiting the formation of dicarbonate to no more than Zppm, where Z is given by log₁₀ (Z)=14.045216-2.4921524 log₁₀ (Mw), and"Mw" is the weight average molecular weight of said polycarbonate,comprising the steps in sequence of (a) contacting Bisphenol-A withphosgene in a reaction mixture containing a solvent and sufficient baseto give such reaction mixture a pH of greater than about 10, therebyforming polycarbonate, and (b) adding para-t-butyl phenol to saidreaction mixture when the heat of said reaction has increased to aconstant level..]..[.21. The process of claim 16, 17 or 19 wherein thedihydroxy compound is Bisphenol-A, Bisphenol-A-P, Tetrabromo Bisphenol-Aor Tetramethyl Bisphenol-A..]..[.22. The process of claim 16, 17 or 19wherein the chain terminator is para-t-butyl phenol, phenol ordi(p-t-butyl) phenol..]..[.23. The process of claim 16, 17 or 19 whereinthe dihydroxy compound is Bisphenol-A and the chain terminator ispara-t-butyl phenol..]..[.24. The composition produced by the process ofclaim 10..]..[.25. The composition produced by the process of claim11..]..[.26. The composition produced by the process of claim12..]..[.27. The composition produced by the process of claim13..]..[.28. The composition produced by the process of claim14..]..[.29. The composition produced by the process of claim15..]..[.30. The composition produced by the process of claim16..]..[.31. The composition produced by the process of claim17..]..[.32. The composition produced by the process of claim18..]..[.33. The composition produced by the process of claim19..]..[.34. The composition produced by the process of claim20..]..[.35. The composition produced by the process of claim21..]..[.36. The composition produced by the process of claim22..]..[.37. The composition produced by the process of claim23..]..[.38. A molded article comprised of a carbonate polymer which isthe product of the reaction of a dihydroxy compound with a carbonic acidderivative and a chain terminator containing a hydroxy group, whicharticle contains only a negligible, insignificant amount ofmonocarbonate..]..[.39. A molded article comprised of a carbonatepolymer which is the product of the reaction of Bisphenol-A withphosgene and para-t-butyl phenol, and which contains only a negligible,insignificant amount of monocarbonate and contains no more than Z ppm ofdicarbonate where Z is given by log₁₀ (Z)=14.045216-2.4921524log₁₀ (Mw),and "Mw" is the weight average molecular weight of saidcomposition..]..[.40. A molded article comprised of a carbonate polymerwhich is the product of the reaction of Bisphenol-A with phosgene andpara-t-butyl phenol, and which contains less than 100 ppm ofmonocarbonate and contains no more than Z ppm of dicarbonate where Z isgiven by log₁₀ (Z)=14.045216-2.4921524log₁₀ (Mw), and "Mw" is the weightaverage molecular weight of said composition..]..[.41. A molded articlecomprised of a carbonate polymer which is the product of the reaction ofa dihydroxy compound, other than Bisphenol-A, with a carbonic acidderivative and a chain terminator containing a hydroxy group, whicharticle contains less than 100 ppm of monocarbonate..]..[.42. A moldedarticle comprised of a carbonate polymer which is the product of thereaction of a dihydroxy compound with a carbonic acid derivative and achain terminator containing a hydroxy group, other than para-t-butylphenol, which article contains less than 100 ppm ofmonocarbonate..]..[.43. A compact disc free of "ghosting" imperfectionscomprised of a carbonate polymer which is the product of the reaction ofa dihydroxy compound with a carbonic acid derivative and a chainterminator containing hydroxy group, which compact disc contains only anegligible, insignificant amount of monocarbonate..]..[.44. A compactdisc free of "ghosting" imperfections comprised of a carbonate polymerwhich is the product of the reaction of Bisphenol-A with phosgene andpara-t-butyl phenol, and which contains only a negligible, insignificantamount of monocarbonate and contains no more than Z ppm of dicarbonatewhere Z is given by log₁₀ (Z)=14.045216-2.4921524log₁₀ (Mw), and "Mw" isthe weight average molecular weight of said composition..]..[.45. Acompact disc comprised of a carbonate polymer which is the product ofthe reaction of Bisphenol-A with phosgene and para-t-butyl phenol, andwhich contains less than 100 ppm of monocarbonate and contains no morethan Z ppm of dicarbonate where Z is given by log₁₀(Z)=14.045216-2,4921524log₁₀ (Mw), and "Mw" is the weight averagemolecular weight of said composition..]..[.46. A compact disc comprisedof a carbonate polymer which is the product of the reaction of adihydroxy compound, other than Bisphenol-A, with a carbonic acidderivative and a chain terminator containing hydroxy group, whichcompact disc contains less than 100 ppm of monocarbonate..]..[.47. Acompact disc comprised of a carbonate polymer which is the product ofthe reaction of a dihydroxy compound with a carbonic acid derivative anda chain terminator containing a hydroxy group, other than para-t-butylphenol, which compact disc contains less than 100 ppm ofmonocarbonate..]..[.48. A composition comprising a carbonate polymerwhich is the product of the reaction of a dihydroxy compound with acarbonic acid derivative and a chain terminator containing a hydroxygroup, which composition is purified of monocarbonate..]..[.49. Acomposition comprising a carbonate polymer which is the product of thereaction of Bisphenol-A with phosgene and para-t-butyl phenol, and whichis purified of monocarbonate and contains no more than Z ppm ofdicarbonate where Z is given by log₁₀ (Z)=14.045216-2.4921524log₁₀ (Mw),and "Mw" is the weight average molecular weight of saidcomposition..]..Iadd.50. The process of claim 10 wherein polycarbonateis formed by passing the reaction mixture through inline mixers in atubular reactor. .Iaddend..Iadd.51. The process of claim 10 whereinpolycarbonate is formed at a pH of at least about
 10. .Iaddend..Iadd.52.The process of claim 10 wherein polycarbonate is formed at a pH of about11 to about
 14. .Iaddend..Iadd.53. The process of claim 10 furthercomprising a step (b') of adding base to the reaction mixture after theaddition thereto of chain terminator and prior to cooling the reactionmixture. .Iaddend..Iadd.54. The process of claim 10 wherein step (c) isperformed in a stirred tank reactor. .Iaddend..Iadd.55. The process ofclaim 10 wherein step (c) is performed by flashing the reaction mixturein a stirred tank reactor. .Iaddend..Iadd.56. The process of claim 10further comprising a step (c') of adding an organic solvent to thereaction mixture after cooling the reaction mixture. .Iaddend..Iadd.57.The process of claim 10 wherein the chain terminator is para-t-butylphenol, phenol or t-octyl phenol. .Iaddend..Iadd.58. The process ofclaim 10 wherein the dihydroxy compound is Bisphenol-A and the chainterminator is para-t-butyl phenol. .Iaddend..Iadd.59. The process ofclaim 10 wherein the chain coupling catalyst is triethylamine..Iaddend..Iadd.60. The process of claim 10 wherein, in step (b), a chainterminator containing a hydroxy group is employed in said reactionmixture such that dicarbonate in excess of Z ppm does not form where Zis given by log₁₀ (Z)=14.045216-2.4921524log₁₀ (Mw), and "Mw" is theweight average molecular weight of said polycarbonate..Iaddend..Iadd.61. The process of claim 10 wherein, in step (b), thereaction between the dihydroxy compound and phosgene is complete whenthe heat of the reaction has increased to a constant level. .Iaddend.